Project description:Genotoxic damage is known to disrupt cellular functions and is lethal if not repaired properly. We compare the transcriptional programs activated in response to genotoxic DNA damage induced by ionizing radiation (IR) in pre-B cells from mice deficient in various DNA damage response (DDR) genes. We used microarrays to detail the global gene expression of mutated cells compared to WT cells, with and without exposure to the DNA damaging agent ionizing radiation (IR), and identified differentially-regulated genes and associated pathways responding to the damage.
Project description:Humans are exposed to ionizing radiation (IR) from background radiation, medical treatments, occupational and accidental exposures. IR causes profound changes in transcription. Transcription is a primary process where protein amount and function can be regulated. One aspect of the transcriptional IR response that little is known about on a whole genome basis is alternative transcription. These investigations focus on the response to IR at the exon level in human cells but also at the whole gene level. Whole genome exon arrays were utilized to comprehensively characterize radiation-induced transcriptional expression products in two human cell types, namely EBV-transformed lymphoblast and primary fibroblast cell lines.
Project description:Eukaryotic cells respond to DNA damage by arresting the cell cycle and modulating gene expression to ensure efficient DNA repair. The human ATR kinase and its homolog in yeast, MEC1, play central roles in transducing the damage signal. To characterize the role of the Mec1 pathway in modulating the cellular response to DNA damage, we used DNA microarrays to observe genomic expression in Saccharomyces cerevisiae responding to two different DNA-damaging agents. We compared the genome-wide expression patterns of wild-type cells and mutants defective in Mec1 signaling, including mec1, dun1, and crt1 mutants, under normal growth conditions and in response to the methylating-agent methylmethane sulfonate (MMS) and ionizing radiation. Here, we present a comparative analysis of wild-type and mutant cells responding to these DNA-damaging agents, and identify specific features of the gene expression responses that are dependent on the Mec1 pathway. Among the hundreds of genes whose expression was affected by Mec1p, one set of genes appears to represent an MEC1-dependent expression signature of DNA damage. Other aspects of the genomic responses were independent of Mec1p, and likely independent of DNA damage, suggesting the pleiotropic effects of MMS and ionizing radiation. The complete data set as well as supplemental materials is available at http://www-genome.stanford.edu/mec1 Set of arrays organized by shared biological context, such as organism, tumors types, processes, etc. Using regression correlation
Project description:NFBD1 (nuclear factor with BRCT domains 1), also known as MDC1 (mediator of DNA damage signaling 1), is a protein involved in the ATM signaling pathway in response to DNA damage. In addition to a role in signaling, NFBD1 possesses transactivation activity, suggesting that it may influence transcription. Furthermore, NFBD1 affects p53-mediated transcription in the presence of the DNA damaging agent adriamycin. Our goal was to determine if NFBD1 affects global gene expression with or without ionizing radiation-induced DNA damage. Moreover, we sought to separate p53-dependent from p53-independent events. Illumina microarray analysis was carried out on RNA extracted from cells treated with and without NFBD1 shRNA and/or p53 shRNA in the presence and absence of DNA damage. Surprisingly, we found that the expression of NFBD1-regulated genes was changed in both the presence and absence of DNA damage. Furthermore, most NFBD1-regulated genes were regulated independently of p53. The identification of NFBD1-regulated genes was confirmed with a second NFBD1-directed shRNA sequence. The role of NFBD1 in global gene expression both in the presence and absence of ionizing radiation was determined. p53-dependent and p53-dependent events regulated by NFBD1 depletion were studied. U2OS cells were treated with control, NFBD1 shRNA, and/or p53 shRNA-expressing retrovirus. Cells were then treated with ionizing radiation and total RNA was isolated for Illumina microarray analysis.
Project description:DNA repair is an essential cellular process required to maintain genomic stability. Every cell is subjected to thousands of DNA lesions daily under normal changes in transcription. Transcription is a primary process where protein amount and function can be regulated. One aspect of the transcriptional IR response that little is known about on a whole genome basis is alternative transcription. These investigations focus on the response to IR at the exon level in human cells but also at the whole gene level. Whole genome exon arrays were utilized to comprehensively characterize radiation-induced transcriptional expression products in two human cell types, namely EBV-transformed lymphoblast and primary fibroblast cell lines.
Project description:Recent observations show that the single-cell response of p53 to ionizing radiation (IR) is “digital” in that it is the number of oscillations rather than the amplitude of p53 that shows dependence on the radiation dose. We present a model of this phenomenon. In our model, double-strand break (DSB) sites induced by IR interact with a limiting pool of DNA repair proteins, forming DSB–protein complexes at DNA damage foci. The persisting complexes are sensed by ataxia telangiectasia mutated (ATM), a protein kinase that activates p53 once it is phosphorylated by DNA damage. The ATM-sensing module switches on or off the downstream p53 oscillator, consisting of a feedback loop formed by p53 and its negative regulator, Mdm2. In agreement with experiments, our simulations show that by assuming stochasticity in the initial number of DSBs and the DNA repair process, p53 and Mdm2 exhibit a coordinated oscillatory dynamics upon IR stimulation in single cells, with a stochastic number of oscillations whose mean increases with IR dose. The damped oscillations previously observed in cell populations can be explained as the aggregate behavior of single cell
Project description:Humans are exposed to ionizing radiation (IR) from background radiation, medical treatments, occupational and accidental exposures. IR causes profound changes in transcription. Transcription is a primary process where protein amount and function can be regulated. One aspect of the transcriptional IR response that little is known about on a whole genome basis is alternative transcription. These investigations focus on the response to IR at the exon level in human cells but also at the whole gene level. Whole genome exon arrays were utilized to comprehensively characterize radiation-induced transcriptional expression products in two human cell types, namely EBV-transformed lymphoblast and primary fibroblast cell lines. 12 human primary fibroblast cell lines and 12 primary lymphoblast cell line samples were used for two doses (0 and 10 Gy) and two time points (0 and 4hr). Additional doses ( 1 Gy, 2 Gy, 5 Gy, and 20 Gy) and time points ( 1hr, 2hr, 8hr, 24hr and 48hr) were assessed in four lymphoblast cell lines and four primary fibroblasts.
Project description:Tardigrades can survive remarkable doses of ionizing radiation, up to about 1000 times the lethal dose for humans. How they do so is incompletely understood. We found that the tardigrade Hypsibius exemplaris suffers DNA damage upon gamma irradiation, but damage is repaired. We show that tardigrades have a specific and robust response to ionizing radiation: irradiation induces a rapid, dramatic upregulation of many DNA repair genes. By expressing tardigrade genes in bacteria, we validate that increased expression of some repair genes can suffice to increase radiation tolerance. We show that at least one such gene is necessary for tardigrade radiation tolerance. Tardigrades’ ability to sense ionizing radiation and massively upregulate specific DNA repair pathway genes may represent an evolved solution for maintaining DNA integrity.
Project description:Eukaryotic cells respond to DNA damage by arresting the cell cycle and modulating gene expression to ensure efficient DNA repair. The human ATR kinase and its homolog in yeast, MEC1, play central roles in transducing the damage signal. To characterize the role of the Mec1 pathway in modulating the cellular response to DNA damage, we used DNA microarrays to observe genomic expression in Saccharomyces cerevisiae responding to two different DNA-damaging agents. We compared the genome-wide expression patterns of wild-type cells and mutants defective in Mec1 signaling, including mec1, dun1, and crt1 mutants, under normal growth conditions and in response to the methylating-agent methylmethane sulfonate (MMS) and ionizing radiation. Here, we present a comparative analysis of wild-type and mutant cells responding to these DNA-damaging agents, and identify specific features of the gene expression responses that are dependent on the Mec1 pathway. Among the hundreds of genes whose expression was affected by Mec1p, one set of genes appears to represent an MEC1-dependent expression signature of DNA damage. Other aspects of the genomic responses were independent of Mec1p, and likely independent of DNA damage, suggesting the pleiotropic effects of MMS and ionizing radiation. The complete data set as well as supplemental materials is available at http://www-genome.stanford.edu/mec1 Set of arrays organized by shared biological context, such as organism, tumors types, processes, etc. Keywords: Logical Set